WASHINGTON — Toni Beth Rosenberg did not think much of it when United Healthcare sent a nurse practitioner to her Boca Raton home as part of a new preventive care program.

The nurse practitioner noticed swelling in her legs and discovered Rosenberg has dangerously high blood pressure. She recommended the 68-year-old see a doctor. He diagnosed Rosenberg with a painful condition than can cause her legs to swell two to three times their normal size. Now she’s getting medication and therapy for the chronic condition.

“I am forever grateful that this happened to me,” Rosenberg said. “I’m not one who runs to a doctor for everything. It just really pushed me, and I’m so grateful.”

The focus on preventive care is among changes Medicare plans are making in response to the Affordable Care Act. While the main focus of the law is on getting more people insured, it also makes significant changes to the popular program that provides health care to seniors.

The law, however, does not force seniors to change plans or enroll in insurance through the online healthcare exchanges. Surveys have found significant confusion among seniors who fear the law will dramatically change their benefits or raise their costs. A survey for Express Scripts found widespread confusion among seniors.

“They don’t understand that Medicare is different and isn’t really changing with the exception that there has been a move to preventative care and more use of medications,” Rebecca Rabbitt, vice president of government programs at Express Scripts, told Bloomberg News. “That message has been lost, if not absent, from a lot of the dialogue.”

The law created a list of preventive screenings, including mammograms and colonoscopies, that must be offered for free to patients.

The law is also slowly shrinking the coverage gap, during which Medicare beneficiaries have to pay for prescriptions on their own. Seniors get discounts on brand name and generic prescription drugs.

The Affordable Care Act gave those who reached the donut hole in 2010 a one-time $250 check. In 2011, it began phasing in the drug discounts. Discounts increase each year until the coverage gap is closed in 2020.

In 2013, the health care law increased the discounts and savings to 52.5 percent of the cost of most brand name drugs and 21 percent of the cost of covered generic drugs.

Since 2010, 6.3 million people with Medicare saved over $6.1 billion, according to the Department of Health and Human Services.

“By making prescription drugs more affordable, the Affordable Care Act is improving and promoting the best care for people with Medicare,” HHS Secretary Kathleen Sebelius said.

While some see the new preventive benefits and drug discounts as a strength of the law, others view it as a waste of taxpayer money.

Ed Haislmaier, a senior research fellow, at the conservative Heritage Foundations, sees two major dangers with the preventive services program. For one, by setting out a list of services insurers must cover at no cost, it could drive them from covering other useful preventive services. And then there’s the argument of cost.

The decision to offer screenings for free “will stimulate greater use of those services, further increasing premiums,” Haislmaier predicts.

The health-care law also seeks to change the program’s reimbursement model for doctors and hospitals. It cuts payments when patients acquire additional illnesses while they are being treated at the hospital for something else. Hospitals also lose money if they readmit patients soon after they been seen for heart failure, heart attack and pneumonia. The law also pays doctors in part on quality measures.

And the health-care law includes new fees for beneficiaries with higher incomes.

If you are single and your income is more than $85,000 annually or you are married and your income is more than $170,000 annually, you may pay higher Medicare premiums, according to the Kaiser Family Foundation, which focuses on health care.

Rosenberg recognizes various changes brought on by the health-care law are unpopular. But she believes the law has already helped her.

For a second year, a nurse practitioner has come to her home. Along with some testing, the practitioner ran through the list of covered preventive testing to check which Rosenberg had.

Critics, like Haislmaier, worry that beneficiaries will be pushed to accept testing they don’t want or need, and that will ultimately increase costs for everyone.

But Rosenberg is sold on the program.

“The Affordable Care Act is all about — first and foremost, in my mind — prevention,” she said.

“If you can prevent somebody from getting really really, really ill that’s going to stop the high medical bills of people going into hospital coming out of the hospital (and) going (back) into the hospital,” she said.